fix(modal, popover): warn if trigger element was not found (#26650)

core/src/components/modal/modal.tsx

@@ -402,8 +402,16 @@ export class Modal implements ComponentInterface, OverlayInterface {
       destroyTriggerInteraction();
     }
 
+    if (trigger === undefined) {
+      return;
+    }
+
     const triggerEl = trigger !== undefined ? document.getElementById(trigger) : null;
     if (!triggerEl) {
+      printIonWarning(
+        `A trigger element with the ID "${trigger}" was not found in the DOM. The trigger element must be in the DOM when the "trigger" property is set on ion-modal.`,
+        this.el
+      );
       return;
     }